Tone adjustment for vibrant bars



arch 1955 P. H. ROWE 2,703,504

TONE ADJUSTMENT FOR VIBRANT BARS Filed Sept. 13, 1949 3 Sheets-Sheet lATTORNEX March 1955 ROWE 2,393,504

TONE ADJUSTMENT FOR VIBRANT BARS Filed Sept. L5, 1949' 3 Sheets-Sheet 2IN V EN TOR.

A TTOR/VE) TONE ADJUSTMENT FOR VIBRANT BARS Filed Sept. 13, 1949 3Sheets-Sheet 3 ZIVVENTOR.

% arra R/VE r United States Patent TONE ADJUSTMENT FOR VIBRANT BARS PaulH. Rowe, Los Angeles, Calif., assignor to Maas- Rowe ElectromnsicCorporation, Los Angeles, Calif., a corporation of CaliforniaApplication September 13, 1949, Serial No. 115,350

10 Claims. (Cl. 84-402) This invention relates to vibrant bars, such,for example, as disclosed in an application filed in the name of Paul H.Rowe on January 7, 1949, under Serial No. 69,658, and entitled:Apparatus for Producing Chime Tones and Method of Tuning Musical Bars.This application is a continuation in part of said prior application.

In the prior application, the bar therein disclosed is made ofrelatively small cross section, such as oneeighth of an inch indiameter, and the ends of the bar were bent so as to extend transverselyof the main body of the bar. The principles disclosed in thisapplication and the prior one, apply to any bar regardless of diameter.The one-eighth inch size was chosen for convenience only. Anyone skilledin the art can apply the teachings of these inventions to bars of otherdiameters. It is therein pointed out that by proportioning the lengthsof the bent ends, it is possible to obtain desirable tone effects,especially to produce accurate octave and double octave tones above thepitch tone of the bar.

It is well known that it is possible to lower the pitch of one mode of abar in relation to other partials by thinning the bar near an antinodeof the mode to be fiattened. Such an arrangement, for example, is shownin the patent Winterhoff, No. 1,632,751 of June 14, 1927.

Generally, the present invention utilizes the principle of altering thecompliance of the bar with bent ends, either by thinning or stiffening;and such a combination of a bent bar with either an increase or decreasein compliance makes it possible to bring the bar readily intosubstantially complete consonance.

It is accordingly an object of this invention to enlarge the scope oftuning the bar to the desired pitch tone or partial tones withoutmaterially adversely affecting the other modes of vibration.

It is another object of the invention to improve the tonal quality of abar of this character by tuning partials other than the first and secondoctaves, such for example as the subtone which is usually approximatelya major sixth below the pitch tone.

It is another object of this invention to provide a simple andinexpensive method and means for substantially accurately tuning theimportant partials of a reso nant bar.

In the usual resonant chime bar or tube, there are five important tonesthat are to be tuned together. There are (1) a pitch tone, which is themost prominent; (2) a subtone intended to be eight semitones below thepitch tone; (3) a first overtone intended to be seven semitones abovethe pitch tone; (4) an octave tone above the pitch tone; and (5) adouble octave above the pitch tone.

By the aid of the present invention, all five modes of vibration can bebrought into substantially accurate tune by first proportioning thebends in a definite manner and then by altering the compliance of thebar either by increasing or decreasing the degree of flexibility of thebar at one or more points in the direction of flexnre during vibration.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of severalforms in which it may be embodied. Such forms are shown in the drawingsaccompanying and forming part of the present specification. These formswill now be described in detail, illustrating the general principles ofthe invention; but it is to be understood that such detailed descriptionis 2,703,504 Patented Mar. 8, 1955 not to be taken in a limiting sense,since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is a side view of a resonant bar which is intended to beexcited (by plucking or striking) to vibrate in a plane parallel to thesurface of the drawing;

Figs. 2, 3, 4, and 5 are views, similar to Fig. 1 of modified forms ofthe invention, parts of the suspension system being omitted;

Fig. 6 is an enlarged fragmentary view of the upper part of the bar; and

Fig. 7 is an enlarged fragmentary view, similar to Fig. 6, of anothermodification.

In Fig. 1, a bar 1 is illustrated made, for example, of metal such ascold rolled steel, and having a short bend 2 at one end and a longerbend 3 at the other end. The bar 1 may be suspended by the aid ofresilient strings 4 and 5 respectively at each end.

When the bar 1 is struck by a force substantially parallel to the planeof the drawing, the bar vibrates in this plane. A pitch tone isproduced, as well as one or more subtones and several overtones.'Usually for a chime tone, the essential tones are (1) the pitch tone;(2) a sub-tone, eight semi-tones below the pitch tone; (3) the firstovertone, which is seven semi-tones above the pitch tone; (4) the octaveof the pitch tone; and (5) the double octave above the pitch tone.

These relationship are not accurate in the ordinary chime tube or bar.By the aid of processes to be described, the pitch tone and these fourpartials can be accurately brought into consonance.

As described in the prior application, the relative lengths of the bentends 2 and 3 with respect to the overall length of the bar 1 before itis bent can be such that the pitch tone and the first and second octavesare in tune. The present process includes as a first step, forming thebar 1 with its ends 2 and 3 in such proportion that the first overtoneabove the pitch tone is in tune with the desired pitch tone. However, inthat case, it is found that the first sub-tone, the pitch tone, andtllile first and second octaves above the pitch tone are too s arp.

For example, with a pitch tone of A-440, a bar made of one-eighth inchdiameter round cold rolled steel can be made as follows: the lower bend3 is .0685 times the unbent length of the bar, and the short upper bend2 is made .039 times the unbent length of the bar. This proportion issubject to minor variations for bars of different length, and may beaffected, to some extent, by different materials and differentdiameters.

In order to compensate for the sharpness of the pitch tone, thesub-tone, and the first and second octaves above the pitch tone, one ormore grooves 10 and 11 are cut in the bar 1. These grooves thin the bar,and are so located as to increase the flexibility of the bar at thesepoints in the direction of flexnre of the vibrations. Such thinninggenerally has the effect of flattening those tones that do not havenodal points at the grooves. The grooves are accordingly so placed thatthey are aligned with the bent ends 2 and 3. These grooves are locatednear the third and fourth nodal points of the first overtone and notnecessarily exactly at these nodal points. The mode of vibration,corresponding to the first overtone, 1s represented by the sinuous line12 to the left of the bar 1. This first overtone has six nodal points13, 14, 15 16, 17, and 18. At these points, the bar does not vibrate inthe first overtone mode. Accordingly, these grooves 10 and 11 havelittle effect on the pitch of the first overtone, which is purposelymade to be quite closely consonant with relation to the desired pitch.

However, since these grooves 10 and 11 fall at points corresponding topoints of vibration for the first subatone, pitch tone, and the firstand second octaves, rthese four modes of vibration are flattened.Sufficient flattening can be obtained by cutting the groove I10 at thethird nodal point :15. I f desired, the groove 11 may -'be near thethird nodal point 16 from the bottom of the bar. The dimensions givenbelow apply to a bar with a single gnoove.

it has been found that the groove may be cut on a radius of one andone-half inches and to a depth corresponding to approximately one-halfthe diameter of the bar 1.

In a specific example, after bending, but before the groove 10 is cut,the pitch tone was found to be of a semi-tone sharp. The first octaveabove the pitch tone was found to be of a semi tone sharp. The secondoctave above the pitch tone was iound to be A of a semi-tone sharp. Thefirst sub-tone, which is to be placed eight semi-tones below the pitchtone, was tound to be of a semi-tone sharp. The [first overtone,intended to be seven semi-tones above the pitch tone, was, in thisinstance, A of a semi-tone sharp. Aiter the groove :10 was cut, it wasfound that all of the overtones were in substantially perfectconcordance.

The length of the bar was chosen to make the first overtone slightlysharp of a semitone) because it was experimentally determined that thebest consonance of all partials is obtained when the groove is cut at apoint slightly toward the end of the bar from the actual nodal point.Accordingly, a very slight flattening of the first overtone is effectedby the groove.

Additional fine tuning can be accomplished by other steps in theprocess. Thus, it the longer bend 3 is shortened by filing, the firstoctave of the pitch tone is sharpened; the pitch tone and the secondoctave above the pitch tone are sharpened substantially equally bnt to aless extent than the first octave. The sub-tone eight semitones belowthe pitch tone is sharpened only to a slight degree. The first overtoneseven semitones above the pitch tone is sharpened least of all.

By reducing the length of the bend 2 by filrn'g, the pitch tone issharpened, the octave above the pitch tone is sharpened to approximatelythe same degree, and the second octave is sharpened to a greater degree.The overtone is sharpened to a lesser degree than the pitch tone, andthe first subtone is sharpened least of all.

It has also been found that the various partials of the bar 1 can beflattened in relation to each other to a. small degree by filing agroove 19 on the inside corner of the bar. In this way, the pitch toneis -very slightly flattened, the double octave partial is flattened to agreater degree, and the first octave is flattened about the same as thepitch tone. The first over-tone is flattened to a degree slightly morethan the pitch tone but considerably less than the second octave. TheSllbniOHfi is barely affected.

The groove in the bar may be located at other of the points in order toproduce tuning effects by increasing the flexibility. Thus, in the termshown in Fig. 2, the bar 20 is shown as having a groove 21 of about thesame proportion as grooves 110 and ill located at or near the centralnode 22 of the pitch tone. When this is done, the first sub-tone will beflattened and the pitch tone will remain relatively constant. The firstovertone will be flattened; land by this means, the sub-tone can bebrought, if desired, to nine semi-tones below the pitch tone, and, byproper adjustment of the length of the bent portions 23 and 24, thedouble octave partials can be kept in tune with the pitch tone. Thepitch tone and the first octave are flattened but slightly by the groove21, since these partials have a node at this point. The double octavepartial is flattened somewhat, but kept sharp by reducing the length ofthe short bend 2/3. A filed groove 19 in the corner of the short bendmay be provided if desired for fine tuning '(see 'Fig. 6). If desired,the groove can be placed at the outside corner, as at 41 of bar 40, asshown in Fig. 7.

In the form shown in "Fig. 3, the bar 25 is similar to the bar 1 shownin Fig.

1, but the groove 26 is now out in the bar at the second nodal bend '14of the first overtone. In this way, the subtone can be loweredto a pointnine semitones below the pitch tone. The bar 25 must be made somewhatsharp before grooving, since the pitch tone is likewise flattened by thegroove 26, but to a slighter degree. Groove 26 improves the relationshipof the first overtone to the pitch tone, since the first overtone is notflattened, while the pitch tone is flattened to 'a considerable degree.Accordingly, the effect is the same as if the first .overtone weresharpened with respect to the pitch tone. In this manner, the firstsubstone, the pitch tone, and the first and second octaves above thepitch tone can be brought into accurate concordance by this method.

The first octave is flattened to the same degree as the pitch tone,whereas the second octave is affected very little. Accordingly, thelength of the bar 25 and the bends 27 and "28 are such as to provide asharp pitch tone and ner of one of the first octave, so that, whenflattened by the grooving operation, these partials will be in tune.

In the torm shown in Fig. 4, the resonant bar 29 can be provided withgrooves 80, 3'1, and 32, corresponding substantially to the second,third, and tourth nodal points of the first overtone. The groove :33 iscut at or near the central nodal point of the pitch tone. in this torm,all of the eflects hereinafter noted may be obtained to a considerabledegree. The filed corner 34, as well as the filing of the ends of thebends '35 and 36, may be utilized to provide finer tuning.

In the forms illustrated in Figs. 1 to 4, of the resonant :bar isaffected solely by thinning the bar at spaced points to increaseflexibility in the direction of vibration. The same effects, however,can be substantially realized by decreasing the flexibility at one ormore definite points. It the stiffness of a vibrating bar is increasedat a given point, the frequencies of all partials requiring the bar toflex at this point will be increased. The degree of frequency increaseis :a direct function of the proximity of an antinode of the particularmode of vibration to the point of increased stillness. On the contrary,if the stiffness is decreased (as illustrated in Figs. 1 to 4) toincrease the compliance the same rule holds good except that now thetrequency is decreased as a direct function of the proximity of ananti-node of that particular mode of vibration to the point of increasedcompliance.

-In Fig. 5, stiifening of the the compliance bar 37 at or near a node ofthe pitch tone is effected by increasing that dimension of the bar whichis in the plane of vibration. This stiflening may complement the use ofthinning at other places such as at 39, in the manner theretoforedescribed. stiffening can be effected, for example, by a forgingoperation flattening the bar at place 38 in a direction trans verse tothe plane of the bent ends. This flattening process increases therigidity (or reduces the compliance) of the bar at the locality 38.Accordingly, all those partials are sharpened in pitch which have nonodes falling at or near the locality 38. On the other hand, the groove39 lowers the pitch of those partials that do not have nodes tailing ator near the groove 39.

Since the bars illustrated in each of the figures are provided withbends at the ends falling in a common plane, these bends serve toconfine vibration substantially entirely to such a plane. In a straightbar, such a stiffening would be impractical since such a straight barvibrates indiscriminately in all planes, and such stiffening wouldproduce undesired beats.

The inventor claims:

1. A resonant bar having bends at each end, and forming end portionsbeyond the bends that extend transversely of the bar, one end portionbeing shorter than the other end portion, said bar having a groove inthe corbends, for flattening at least some of the tone partials of thebar.

2. A resonant bar having end portions bent transversely to the bar; oneend portion being substantially twice as long as the other end portion;said bar having a stiffened portion intermediate the ends, the stiffenedportion being such as to decrease flexibility in the plane of vibration.

3. A resonant bar having end portions bent transversely to the bar; oneend portion being substantially .068 of the total length of the bar, andthe other end portion being substantially .039 of the total length ofthe bar; said bar having a stiffened portion near a nodal point of oneof the modes of vibration of the bar.

4. A resonant bar having a bend near one end thereof forming an endportion extending transversely of the bar, and having a groove in acorner of the bend.

5. resonant bar having a bend at one end, forming a portion extendingtransversely of the bar; said bar having a thin portion intermediate theends of the bar, there being a minimum thickness dimension transverse tothe bar at said thin portion that is substantially in the direction ofsaid end portion, to provide flexibility in said direction.

6. A resonant bar having bends at each end, and forming end portionsextending in the same direction transversely of the bar; said bar havinga thin portion intermediate the ends of the bar, there being a minimumthickness dimension transverse to the bar at said thin portion that issubstantially in the direction of said end portions, to provideflexibility in said directon.

7. A resonant bar having a bend at one end, forming a portion extendingtransversely of the bar; said bar havhaving a thin portion intermediatethe ends of the bar, the thin portion serving to reduce the thickness ofthe bar, there being a minimum dimension transverse to the bar at saidreduced thickness that is substantially in the direction of said endportion, to provide flexibility in said direction.

8. A resonant bar having a bend at one end, forming a portion extendingtransversely of the bar; said bar having a thin portion intermediate theends of the bar, the thin portion serving to reduce the thickness of thebar, the dimension of reduced thickness being substantially in thedirection of the end portion.

9. A resonant bar having a bend at one end, forming a portion extendingtransversely of the bar; said bar having a plurality of thin portionsintermediate the ends of the bar, there being, for each thin portion, aminimum thickness dimension transverse to the bar at said thin portionthat is substantially in the direction of said end portion, to provideflexibility in said direction.

10. A resonant bar having a bend at one end, forming a portion extendingtransversely of the bar; said bar having a plurality of thin portionsintermediate the ends of the bar, the thin portions serving to reducethe thickness of the bar, the dimension of reduced thickness for each ofthe thin portions being substantially in the direction of the endportion.

References Cited in the file of this patent UNITED STATES PATENTS137,643 Witney et al. Apr. 8, 1873 491,607 Steck Feb. 14, 1893 644,817Deagan Mar. 6, 1900 793,300 Junghans June 27, 1905 1,632,751 WinterhoffJune 14, 1927 1,838,502 Schluter Dec. 29, 1931 1,999,355 Curtiss Apr.30, 1935 2,180,110 Hultsch Nov. 14, 1939 2,273,333 Schluter Feb. 17,1942 2,413,062 Miessner Dec. 24, 1946 2,454,402 Okrain Nov. 23, 19482,542,540 Kunz Feb. 20, 1951 2,581,963 Langloys Jan. 8, 1952 2,588,295Rowe Mar. 4, 1952

